1. Field of the Invention
The present invention relates to an ink jet print head that ejects ink onto a print medium to form an image on it.
2. Description of the Related Art
FIG. 9 to FIG. 11 show a construction of a conventional ink jet print head. FIG. 9 and FIG. 10 are perspective views of the entire ink jet print head as seen from an electric wiring member side and from an ink ejection member side, respectively. FIG. 11 is a front view of the print head as seen from the ink ejection member side, penetratively showing ink paths and ink supply ports.
As shown in FIG. 9 and FIG. 10, an ink jet print head 200 comprises an ink supply member 201, a flow path plate 202, an ink ejection member 203 and an electric wiring member 204 all formed integral as one body. On the ink supply member 201 are removably mounted a first ink tank 206a, a second ink tank 206b and a third in tank 206c.
On the ink ejection member 203 is arranged an orifice plate (not shown) formed with a plurality of ejection opening columns to eject ink as ejection energy generation elements such as electrothermal transducers are driven. The ink ejection member 203 is provided with a plurality of ink supply ports (five ports in the example shown) one for each of the ejection opening columns. The individual ejection energy generation elements are supplied a drive signal through contact pads 204a of the electric wiring member 204 that are in contact with a connector (not shown) on the printing apparatus side.
As shown in FIG. 11, the five ink supply ports 203a, 203b, 203c, 203d and 203eprovided in the ink ejection member 203 are arranged so that their direction of array is parallel to that of the first, second and third ink tanks 206a, 206b and 206c. The flow path plate 202 is formed with ink paths to supply ink from ink introduction holes of the ink tanks to the respective ink supply ports. An ink path 201d running from an ink introduction hole 201a of the first ink tank 206a connects to two ink supply ports 203a and 203e situated at the ends, in the array direction, of the group of the ink supply ports. An ink path 201e running from an ink introduction hole 201b of the second ink tank 206b connects to two ink supply ports 203b and 203d situated on both sides of the center ink supply port 203c. Further, an ink path 201f running from an ink introduction hole 201c of the third ink tank 206c connects to the center ink supply port 203c. Thus, the five ink supply ports 203a, 203b, 203c, 203d, 203e are supplied, from one end of the port group in the array direction, first color, second color, third color, second color and first color in a symmetrical color order.
As described above, the ink jet print head 200 of the above construction has five ink supply ports and five ejection opening columns in the ink ejection member 203 arranged in a symmetrical order of colors although there are only three color ink tanks. Therefore, when the print head is mounted on a carriage of the ink jet printing apparatus for reciprocal printing on a print medium, the same color ink application order can be realized for both a first main scan in a forward direction and a second main scan in a backward direction. This suppresses color deviations assuring a good print quality. That is, this control of the reciprocal printing operation can not only increase the printing speed but also enhance the print quality.
In the construction of the ink jet print head described above, five ejection opening columns are used although there are only three color inks. It is therefore necessary to arrange the ink paths to the individual ink supply ports so that they do not cross each other in a plane while minimizing the number of ink tanks (three). When penetratively viewed from the ink supply port side, the ink paths of other colors overlap some of the ink supply ports, as shown in FIG. 11.
Therefore, the ink paths are narrow and complex, and communication portions between the ink paths and the ink supply ports are limited by the ink paths of other colors and thus inevitably become relatively small holes.
In such an ink path construction, there is little problem in supplying ink from the ink tanks to the ink ejection member. However, if an ink jet printer is left unused for a long period of time, air dissolved in ink may become separated from the ink or external air may enter penetrating through the flow path plate 202 that forms the ink paths. In that case, bubbles may accumulate in the ink paths of the ink jet print head and are not easy to draw out from the narrow, complicated ink paths.
Generally, the ink jet printing apparatus is provided with means for processing to recover or maintain an ink ejection performance of the ink jet print head. One such example is means for performing a suction-based recovery operation, which involves capping a surface of the print head formed with ink ejection openings and, in the capped state, applying a negative pressure to the ejection openings to forcibly discharge ink from ink paths inside the ejection openings. If the ink paths are narrow and complex as described above, the control of the suction pressure and suction time during the suction-based recovery operation requires precise adjustments.